It's not uncommon for people to read just before going to sleep, sometimes even enjoying such downtime from the comfort of their own bed. However, if that reading material is in the form of a light-emitting e-reader book (LE-eBook) rather than a printed book, it can be detrimental to overall health.

The finding comes from researchers at Brigham and Women's Hospital (BWH) who examined the relationship between participants' before-bedtime reading habits (electronic versus a printed book) and resulting health consequences.

"We found the body's natural circadian rhythms were interrupted by the short-wavelength enriched light, otherwise known as blue light, from these electronic devices," said Anne-Marie Chang, PhD, corresponding author of the study which was published in the Proceedings of the National Academy of Sciences. "Participants reading an LE-eBook took longer to fall asleep and had reduced evening sleepiness, reduced melatonin secretion, later timing of their circadian clock and reduced next-morning alertness than when reading a printed book." Chang is also an associate neuroscientist in BWH's Division of Sleep and Circadian Disorders.(1)

What happens when people use their laptops and cell phones before bedtime

For the study, a group of participants read LE-eBooks on an iPad four hours every night for five nights in a row. The researchers also analyzed the impact of other kinds of blue-light-emitting electronic devices such as laptops, cell phones and laptops. The process was also analyzed with printed books.

It was found that those who read the iPad not only took longer to fall asleep but also didn't remain in REM sleep as long as they should and that they also had reduced melatonin secretion, which is an important hormone to help sleepiness occur.

Additionally, those who read such electronic devices before going to sleep had delayed circadian rhythms which were found to be off by more than an hour. Finally, while people who read this way felt less sleepy before going to bed, they reported feeling less alert and more tired the next morning -- even after receiving eight hours of sleep.

The study, titled "Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness," provides further elaboration as to why this occurs:

Mounting evidence from countries around the world shows the negative impact of such technology use on sleep. This negative impact on sleep may be due to the short-wavelength-enriched light emitted by these electronic devices, given that artificial-light exposure has been shown experimentally to produce alerting effects, suppress melatonin, and phase-shift the biological clock.(2)

The published study sums up the findings and health implications as follows:

Participants reading an LE-eBook took longer to fall asleep and had reduced evening sleepiness, reduced melatonin secretion, later timing of their circadian clock, and reduced next-morning alertness than when reading a printed book. These results demonstrate that evening exposure to an LE-eBook phase-delays the circadian clock, acutely suppresses melatonin, and has important implications for understanding the impact of such technologies on sleep, performance, health, and safety.(2)

The link between the body's circadian clock and onset of diabetes and heart attacks

These findings don't just suggest that people should put their electronic devices away so that they are alert the next day. While that is true according to this study, their other discoveries have more far-reaching heath implications. For example, when it comes to the circadian rhythm, previous studies have found that disruptions in it can wreak havoc on the body's insulin levels and ultimately lead to obesity, heart attacks and diabetes.

One such study was conducted by researchers at Vanderbilt University who determined that insulin operates on a 24-hour cycle and that, when there are upsets in the body's circadian clock, it's ability to protect health is compromised. Disruptions in this clock can involves changes in sleep as well as eating habits.(3)

While people's portable devices make it easy to relax and read or browse in the hours before bedtime, it might be wise to limit the activity. It might be hard to put that interesting e-book down or to refrain from scrolling through social media posts, but it would appear that better health depends on it.

About the author:A science enthusiast with a keen interest in health nutrition, Antonia has been intensely researching various dieting routines for several years now, weighing their highs and their lows, to bring readers the most interesting info and news in the field. While she is very excited about a high raw diet, she likes to keep a fair and balanced approach towards non-raw methods of food preparation as well.

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